Chemical and Biological Perspectives of Monoterpene Indole Alkaloids From Rauwolfia species

The biosynthesis of monoterpene indole alkaloids (MIAs) starts with a geraniol for the terpenoid portion. Secologanin, a secoiridoid glycoside, is derived from 10-hydroxygeraniol, produced in the presence of geraniol 10-hydroxylase. The indole portion of MIAs contain tryptamine, produced by the decarboxylation of tryptophan. Conjugation of secologanin with tryptamine is achieved with strictosidine synthase to produce strictosidine. Over 2500 known MIAs found in many plants from several families, such as Apocynaceae, Loganiaceae, Rubiaceae, and Nyssaceae, are produced by modification of strictosidine. A number of pharmacologically active compounds, namely, reserpine, ajmalicine, ajmaline, serpentine, and yohimbine, isolated from different Rauwolfia species, are examples of MIAs